2004 Toyota Tundra Base, AutomaticFACTORY OEM SERVICE PROCEDURE

Circuit Opening Relay: Inspection

  1. REMOVE RELAY BOX COVER 
  2. REMOVE CIRCUIT OPENING RELAY (Marking: C/OPN) 
    Fig 1: Removing Relay Box Cover
    G04207993Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  3. INSPECT CIRCUIT OPENING RELAY 
    1. Inspect the relay continuity.
      1. Using an ohmmeter, check that there is continuity between terminals 1 and 2.

        If there is no continuity, replace the relay.

      2. Check that there is no continuity between terminals 3 and 5.

      If there is continuity, replace the relay.

      Fig 2: Checking Continuity Between Terminals 1 And 2
      G04207994Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Inspect the relay operation.
      1. Apply battery positive voltage across terminals 1 and 2.
      2. Using an ohmmeter, check that there is continuity between terminals 3 and 5.

      If there is no continuity, replace the relay.

  4. REINSTALL CIRCUIT OPENING RELAY 
  5. REINSTALL RELAY BOX COVER 
    Fig 3: Checking Continuity Between Terminals 3 And 5
    G04207995Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Chapter Navigation
Return to Chapter: Circuit Opening Relay
Factory Service Tools

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.

Shop Manual-Ready ToolsCompare Repair QuoteQuote Shield Pro

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.